Expanded structural members

ABSTRACT

A method of forming an expanded structural member, and a structural member formed thereby, wherein spaced parallel longitudinally extending rows of openings are pierced in a web of a member of ductile metal which has a constant cross-sectional shape, the openings of each row overlapping those of the next adjacent row so as to form a series of strut forming elements in the web, forcing the parallel edges of the member apart so as to stretch the elements and thus form struts, the edge portions thereby becoming chords, and positioning load transmitting members between chords so as to transmit load imposed on one of the chords to the other chord.

United States Patent 1 1 1111 3,737,964 Jury June 12, 1973 [54] EXPANDEDSTRUCTURAL MEMBERS 3,364,646 1/1968 Snider 52/690 1,791,680 2/1931Miller 52/690 [75] gfi' 't g g Jury 1,899,344 2/1933 Macomber 52/690 x[73] Assignees Jury & Spiers Proprietary Limited, P i E i Th H, EagerNQTW0AuStfa1la Attorney-Albert H. Oldham, Vern L. Oldham and 22 Filed:July 27, 1971 Edwm Oldham 21 Appl. No.: 166,390

[57] ABSTRACT 30 Foreign A li tio priority Data A method 06 forming anexpanded structural member, Jul 31 1970 Australia 2042 and a structuralmember formed thereby, wherein y spaced parallel longitudinallyextending rows of open- [52] U 8 Cl 29/155 R 29/6 1 52/635 ings arepierced in a web of a member of ductile metal 51 IntICIII IIIIIIII II:1125; 17 00 which has a wnstam cmss'sectional Shape the 58 Field 61Search 52/635, 696, 690, P of "1 52/636, 692495; 29/61, 155 R, 155 C rowso as to form a series of strut forming elements 1n the web, forcing theparallel edges of the member apart [56] References Cited so as tostretch the elements and thus form struts, the

edge portions thereby becoming chords, and position- UNITED STATESPATENTS ing load transmitting members between chords so as to transmitload imposed on one of the chords to the other a mer.... 1,571,2382/1926 Domier 52/692 10 Claims, 8 Drawing Figures PATENIEU JUN] 2 I975SHEET 2 OF 3 EOT EXPANDED STRUCTURAL MEMBERS This invention relates toimprovements in expanded structural members wherein truss-like membersare formed as spaced outer chords interconnected by a plurality ofstruts.

If a structural member is formed by a method which includes firstlyforming a member of ductile metal having a constant cross-sectionalshape which comprises a pair of spaced parallel longitudinally extendingedge portions and a web joining those web portions, and the web ispierced with a plurality of spaced partly longitudinal rows of openingswhich overlap one another, and

the deformable elements of the web between the edge portions arestrained to form a series of inclined struts, then a structural girderof lattice or-half lattice type is formed which is suitable for loadbearing. One of the requirements of such a girder is that the metalshould be sufficiently ductile to allow the struts to be formed byelongating, the elongation process normally being a simple strainingprocess, and elongation beyond the yield point, while hardening themetal forming the struts, nevertheless can result in a slight degree ofnecking", thatis, reduction in diameter at a localised point. Thus thefactor of safety should be increased beyond that normally used for agirder of similar configuration and dimension but made by a fabricatingprocess, although even with an increase of factor of safety the cost ofproduction is very small. If such a girder is tested to destruction,destruction will occur due to buckling of the chords which are incompression or of the struts which are in compression. As is well knownin the art the shear loading on the girder or truss is resisted bytransformation into compressive and tensile forces in the elementswhich'define the triangles of the truss.

When a truss is formed from a unitary piece of metal by the methodbriefly described above, quite clearly it is. desirable that the metalsection should not be excessively massive because of the amount of forcerequired to elongate the .strut forming portions of the web.

Thus there are at least two reasons why'the buckling loads on the chordsand struts should be as small as possible for a given trussconfiguration, and the main object of this invention is to provide amethod of forming a truss whereby the buckling forces are, substantiallyreduced, and in one of its forms the invention consists of the method offorming an expanded structural member which comprises forming a memberof ductile metal having a constant cross-sectional shape which comprisesa pair of spaced parallel longitudinally extending edge portions and aweb joining the edge portions, at least partly piercing at least twospaced parallel longitudinally extending rows of openings in the web,the openings of each row overlapping thoseof the next adjacent row so asto form therebetween a series of deformable elements of the webinterconnected by junction portions, urging the edge portions apart soas ,to extend the lengths of the deformable elements to 'ship with theflanges to thereby transmit at least portion ofa load imposed on one ofthe chords in the direction of the other chord to said other chordthrough said load transmitting member.

The invention also relates to an expanded structural member which isformed by the method of the invention, and comprises chords and strutsof a unitary piece of metal and load transmitting members extendingbetween the chords where they are joined to struts. As is shownhereunder, the existence of these load transmitting members will reducethe buckling loads very considerably if the load transmitting membersare stiff spacer members which extend between the chords of the truss totransmit load from a first chord to a second chord at the location ofthe intersection of the struts with the second chord, or if they areplates which engage the chords along their edges.

The invention is described hereunder in further detail with reference toand is illustrated in the accompanying drawings in which:

FIG. 1 is a perspective view showing a member of ductile metal having aconstant cross-sectional shape but having been pierced with three spacedparallel longitudinal rows of openings in its web,

FIG. 2 is a side elevation showing the member ofFIG. 1 after the edgeportions thereof have been urged apart to form chords and tosimultaneously extend the lengths of deformable elements of the webs andthus form them into struts inclined to the chords, FIG. 2 showing indotted lines one mode of inserting load transmitting members between thechords,

FIG. 3 is a section taken on line III-Ill of FIG. 2 wherein the loadtransmitting member is represented as a stiff spacer of timber,

FIG. 4 is a section on line IVIV of FIG. 2 illustrated as the loadtransmitting member, a stiff spacer member formed from square sectiontube,

FIG. 5 is a schematic diagram showing the tensile and compressive forcesin a half lattice girder when used as a beam, loaded from the top andsupported at its ends from the bottom,

FIG. 6 is a similar diagram of the same half lattice girder wheninverted, under the same loading and similarly supported, the halflattice girder however being modified with stiff spacer members, FIG. 6then showing loadings which may be compared with those of FIG. 5, i

FIG. 7 is a partly sectioned perspective view showing a furtherembodiment wherein the load transmitting members are formed bycontinuous plates, and

FIG. 8 shows a still further embodiment wherein the load transmittingmembers are formed by stiff spacer members of timber, and wherein thechords also contain timber, FIG. 8 being a truss suitable for use inbuildings.

The first embodiment refers to FIGS. 1, 2, 3 and 4, and in FIG. 1 amember 30 of ductile metal is formed by an extrusion process, in thisembodiment the metal being a.ductile grade of aluminium alloy. Themember has edge portions constituted by flanges 31 which areinterconnected by a web 32, the web 32 having extending along it a pairof ribs 33, and a series of openings 34 are pierced in the web 32, therebeing three rows of openings 34 one between the ribs 33 and one on eachside of each of the ribs. The openings of each row overlap as shown inFIG. I so as to form those portions of the ribs 33 which lie between theoverlapping portions of the openings 34 into a series of deformableelements which are designated 35.

FIG. 2 shows the next stage in the formation of the truss wherein theflanges 31 are urged apart so as to thereby strain the deformableelements 35 beyond their yield point, lengthening them and forming theinclined struts 36, the struts 36 being interconnected by junctionportions 37 which also interconnect the struts 36 to the web 32 asillustrated in FIG. 2, the flanges 31 then becoming the chords of thetruss so formed. It will be noted that the central axes of the struts 36intersect,

and it is important to arrange the length of junction portions 37 sothat this will occur.

In this invention the flanges 31 have interposed between them a seriesof load transmitting members, and FIG. 3 illustrates one form which theload transmitting members may take. In FIG. 3 the load transmittingmember is a stiff spacer member 40 which has grooves 41 in its upper andlower ends, the grooves 41 being positioned over the ribs 33 where theyare joined to the web 32 by the junction portions'37. Fastening members42 secure the ends of the stiff spacer members 40 against possibledisplacement. The spacer members 40 are positioned as shown to havetheir ends over the junction portions 37 in order to avoid placingbending moments on those portions of the flanges 31 which areunsupported by the struts 36. The struts 36 are inclined as shown inFIG. 2 at an angle of less than 45 to the flanges 31 so that the spacesdesignated 43 are of diamond shape have greater length than height andthis enables the spacer members 40 to be inserted and then rotated, themembers 40 thus being easily positioned between the flanges 31.

The slight variation of structure illustrated in FIG. 4 is useful whenan all metal construction is required, and the stiff spacer member 45 isa tubular member formed from square section tube again having grooves 41positioned'over the ribs 33 and the junction portions 37. Rivets 46secure the ends of the spacer member 45 against displacement.

The advantage of the invention is shown by comparing the loadings in thechords and struts, FIG. 5 showing a load of thirty kilograms dividedinto three equal portions of the junction portions between the strutsand top chord of a half lattice girder which can be formed readily bythis invention, and it will be seen that the end struts designated 49each carry a compressive loading of twenty-five kilograms while the topchords designated 50 each carry a compressive loading of 26.6 kilograms.The figures shown alongside each of the elements of the chords and eachof the struts indicate respective loadings and the letters and tindicate compressive and tensile stresses respectively. If FIG. iscompared with FIG. 6, it will be seen that the maximum compressiveloading in the struts is 10.7 kilograms in each of the struts designated51, although the maximum compressive loading in the upper chords 52remains substantially unaltered. This reduction of loading is achievedby the stiff spacer members which are all designated 54 in FIG. 6.

In FIG. 7 which illustrates a further embodiment of the invention, theexpanded structural member generally designated 57 includes upper andlower flanges 58 and 59 respectively and an intermediate strut 60, theflanges 58 and 59 being joined by the struts 60 as in the otherembodiments. The upper and lower flanges however each have inwardlyfacing beads 61 arranged in two pairs in each flange and definingbetween them four channels, channels on respective sides of the strut 60retaining upper and lower edges of a shear plate 62 on each side, theshear plate 62 being inserted by straining the intermediate struts 60,positioning each shear plate 62 in its respective lower channel, andreleasing the strain on the struts so that the resilience thereof drawsthe other channels into engagement with the other edges of the shearplates 62. The advantage of the structure which is illustrated in FIG. 6is even greater when the load transmitting members are shear plates asshown in FIG. 7, and the load on the shear plates is so small thatdecorative panels in some instances are used.

In many building operations it is desirable to provide timber verticaland horizontal members for the fixing of roofing purlins or otherscantlings, and in the further embodiment illustrated in FIG. 8, theflanges again designated 31 are interconnected by inclined struts 36 asin the embodiment of FIG. 2, the struts 36 being joined together andalso being joined to the web 32 by the junction portions 37. The flanges31 however have upstanding edges which perform the dual function ofretaining timber chord inserts 66 and also stiffening and strengtheningthe chords which are constituted by the flanges and the inserts. Theload transmitting members are again stiff spacer members 67 each formedin two portions joined together by fastening means 68, the members 67also being of timber and extending for the full width of the flanges 31so as to facilitate securing of other structural or decorative membersrequired.

In all the above embodiments the member of constant cross-section hasbeen described as having openings pierced therethrough. The openingsneed not be completely pierced, but if desired the slugs formed bypiercing of the openings may be only partly sheared, and removed uponthe urging of the edge portions apart. In all cases the edge portionsare urged apart by clamping between jaws which themselves are drivenapart under hydraulic pressure.

It should be noted that difference in truss configuration, strut length,or loading will produce substantial variations to the loadings shown inFIGS. 5 and 6.

What I claim is:

1. The method of forming an expanded structural member which comprisesextruding a member of ductile metal having a constant cross-sectionalshape which comprises a pair of spaced parallel longitudinallyex-tending edge portions, a web joining the edge portions, and at leastone rib extending along the web,

at least partly piercing at least two spaced parallel longitudinallyextending rows of openings inthe web, each opening being a slot havingparallel sides and curved ends, the openings of each row overlappingthose of the next adjacent row so as to form therebetween a series ofdeformable elements of the web interconnected by junction portions, saiddeformable elements each comprising portion of a said rib,

urging the edge portions apart so as to extend the length of thedeformable elements to thereby form struts and form chords of the edgeportions,

and positioning at least one load transmittingmember between the chords,and securing opposite ends of the load transmitting member in loadtransmitting relationship with the chords to thereby transmit at least aportion of a load imposed on one of the chords in the direction of theother chord to said other chord through said load transmitting member.

2. The method according to claim 1 wherein said load transmitting memberis a plate, and the method comprises the further step of securing theplate along two opposite edges to respective edge portions.

3. The method according to'clai'm 2 wherein said chords comprise flangeseach having two pairs of inwardly directed beads with a pair on eachside of said struts, each pair of inwardly directed beads forming achannel therebetween, said method comprising the further step ofstraining the struts, positioning each of two said plates between thechannels on respective sides of the struts, and releasing the strain onthe struts whereby the resilience of the struts retains the edges of theplates in respective channels.

4. The method according to claim 1 wherein each load transmitting memberis a stiff spacer member extending between the chords, the methodfurther comprising engaging at least one end of each load transmittingmemberv with one of the chords at the location of a junction portionbetween that chord and a said strut.

5. The method according to claim 4 wherein flanges comprise said chords,the method further comprising interpositioning each said stiff spacermember between the flanges and securing it thereto.

6. The method according to claim 4 wherein each spacer member containsgrooves in its ends, the method further comprising positioning thegrooves over the struts at the location of junction portions between thestruts and the edge portions.

7. The method according to claim 4 wherein said spacer members areformed of timber.

8. The method according to claim 4 wherein said spacer members areformed of tubular metal having a square cross-sectional shape.

9. The method according to claim 1 wherein the edge portions arechannels which contain timber.

10. The method according to claim 1 comprising at least partly piercingmore than two said spaced parallel longitudinally extending rows ofopenings in the web to thereby form a plurality of said series ofdeformable elements of the web interconnected by said junction portions,and urging the edge portions apart so as to extend the lengths of thedeformable elements to thereby form a plurality of .strutsinterconnected by said junction portions and having the central axes ofthe struts intersecting in the junction portions.

1. The method of forming an expanded structural member which comprisesextruding a member of ductile metal having a constant cross-sectionalshape which comprises a pair of spaced parallel longitudinallyex-tending edge portions, a web joining the edge portions, and at leastone rib extending along the web, at least partly piercing at least twospaced parallel longitudinally extending rows of openings in the web,each opening being a slot having parallel sides and curved ends, theopenings of each row overlapping those of the next adjacent row so as toform therebetween a series of deformable elements of the webinterconnected by junction portions, said deformable elements eachcomprising portion of a said rib, urging the edge portions apart so asto extend the length of the deformable elements to thereby form strutsand form chords of the edge portions, and positioning at least one loadtransmitting member between the chords, and securing opposite ends ofthe load transmitting member in load transmitting relationship with thechords to thereby transmit at least a portion of a load imposed on oneof the chords in the direction of the other chord to said other chordthrough said load transmitting member.
 2. The method according to claim1 wherein said load transmitting member is a plate, and the methodcomprises the further step of securing the plate along two oppositeedges to respective edge portions.
 3. The method according to claim 2wherein said chords comprise flanges each having two pairs of inwardlydirected beads with a pair on each side of said struts, each pair ofinwardly directed beads forming a channel therebetween, said methodcomprising the further step of straining the struts, positioning each oftwo said plates between the channels on respective sides of the struts,and releasing the strain on the struts whereby the resilience of thestruts retains the edges of the plates in respective channels.
 4. Themethod according to claim 1 wherein each load transmitting member is astiff spacer member extending between the chords, the method furthercomprising engaging at least one end of each load transmitting memberwith one of the chords at the location of a junction portion betweenthat chord and a said strut.
 5. The method according to claim 4 wherEinflanges comprise said chords, the method further comprisinginterpositioning each said stiff spacer member between the flanges andsecuring it thereto.
 6. The method according to claim 4 wherein eachspacer member contains grooves in its ends, the method furthercomprising positioning the grooves over the struts at the location ofjunction portions between the struts and the edge portions.
 7. Themethod according to claim 4 wherein said spacer members are formed oftimber.
 8. The method according to claim 4 wherein said spacer membersare formed of tubular metal having a square cross-sectional shape. 9.The method according to claim 1 wherein the edge portions are channelswhich contain timber.
 10. The method according to claim 1 comprising atleast partly piercing more than two said spaced parallel longitudinallyextending rows of openings in the web to thereby form a plurality ofsaid series of deformable elements of the web interconnected by saidjunction portions, and urging the edge portions apart so as to extendthe lengths of the deformable elements to thereby form a plurality ofstruts interconnected by said junction portions and having the centralaxes of the struts intersecting in the junction portions.